Barometer.



PATENTED NOV. 28, 1905.

A. H. MOGONNELL.

BAROMETER. APPLIUATION FILED JAN.7.1905.

UNITED vSTATES PATENT OFFICE.

ALEXANDER H. MCCONNELL, OF WILMETTE, ILLINOIS, ASSIGNOR TO CENTRALSCIENTIFIC COMPANY, A CORPORATION OF ILLINOIS.

BARONIETER.

Specification of Letters Patent.

Patented Nov. 28. 1905.

Application filed anuary '7, 1905. Serial Noc 240,062.

T0 all whom it 771,614/ concern:

Be it known that I, 1ALEXANDER H. Mc- CONNELL, a citizen of the UnitedStates, and a resident of Wilmette, county of Cook, and State ofIllinois, have invented certain new and useful Improvements inBarometers, of which the following is a specification and which areillustrated in the accompanying drawings, forming a part thereof.

This invention relates to an instrument for measuring the pressure ofgases in general, but particularly for measuring the pressure of theatmosphere. When especially constructed for this latter use theinstrument is universally known as a barometen The obj ect of theinvention is to simplify the construction of instruments of the kinddescribed and so improve them that they shall be less susceptible to thechanges in the temperature and humidity of the atmosphere, which changestend to vitiate the results of the measurements obtained.

The inventionconsists in the construction and arrangement of parts to behereinafter described and which are illustrated in the accompanyingdrawings, in which- Figure I is a front elevation of a barometerconstructed in accordance with the invention. Fig. 2 is a detailvertical section on the line 2 2 of Fig. 4. Fig. 3 is a detail sectionon the line 3 3 of Fig. 4. Figs. 4, 5, and 6 are sectional views on thelines 4 4, 5 5, and 6 6, respectively, of Fig. l; and Fig. 7 is similarto Fig. 3, but showing a modification in the construction.

Instruments of the class to which that forming the subject of theinvention belongs consist of a glass tube of considerable length whosebase dips into a reservoir containing mercury and within which themercury rises to a height varying with the pressure upon the surface ofthe mercury in the reservoir. When the device is intended for measuringthe pressure of the atmosphere, the glass tube is closed at the top, andso much of the interior of the tube as is not filled bythe mercury is avacuum. As frequently constructed, this reservoir is provided with aflexible bottom, which may be raised or lowered in order to bring thesurface of the mercury in the reservoir to some predetermined level,permanently marked, which coincides with the zero point or base for ascale of units of length,

such as inches or centimeters, indicated along the side of the tube for4as much of its length as will include the range of movement of the topof the mercury column when the instrument is in use. A supporting meansis usually provided to which the tube and reservoir are permanentlyattached in order that the device maybe portable. In the drawings suchsupporting means is shown as a wall-plate I0, to which the glass tube l1is attached by means of the cleats l2 12. The scale is marked upon aplate I3, preferably of metal, secured to the wall-plate 10 behind thebarometer-tube and of sufficient length to contain the propergraduations for indicating the height of the mercury columncorresponding to the most eXtreme fluctuations in pressure to bemeasured. The base of the tube 11 enters a reservoir or inverted cup 14,which in the present instance is of glass and is formed integral withthe walls of the tube and incloses its lower end. The wall-plate 10 iscut away below, as indicated at 15, to receive the reervoir and permitthe tube 1I to lie close aganist its face. The lower edge of thereservoir is preferably flanged outwardly, as at 16, and there isprovided a metal ring 17 of the proper size to surround the reservoirand bear upon this flange 16. The reservoir is closed by a sack 18, ofsome flexible material impervious to mercury, as leather. The rim ofthis sack is firmly bound to the flange 16 at the lower edge of thereservoir by the gripping action of the ring I7 and a flange 19 of abase-plate 20, which are drawn together by a plurality of set-screws 2l,passing through recesses 16a in the rim of the flange 16. The ring 17 islined with a washer 22 in order that it may seat itself upon the glassflange. The base-plate 20is chambered to receive the flexible sack 18,and is provided with wings 23 23, by means of which it may be secured tothe wall-plate l0; A set-screw 24 enters the base-plate from below andis capped by a swiveled disk 25, which bears against the central portionof the flexible sack.

A downwardly-projecting. permanent indicator-point A26, from the tip ofwhich the graduations on the scale-plate 13 are measured, is providedwithin the chamber of the reservoir. It is formed of glass and isintegral with the wall of such chamber. In Fig. 3 it is shown as formedupon the outer sur .TOO

face of the tube 11, while in Fig. 7 it is shown as formed upon theinner surface of the outer wall of the reservoir 14.

As is usual in instruments of this kind, a Vernier is'provided whichcoperates with the scale marked upon the plate 13 for obtaining anaccurate reading of the height of the mercury column within the tube. lnthe preferred construction this vernier comprises a sliding block 27,dovetailed into the plate 13, as most clearly shown in Fig. 6, andhaving a tubular boss 28, which incloses the barometer-tube and has onits forward side a downwardly-extending lip formed into a horizontalknife-edge 29. This vernier is graduated, as is customary in devices ofthis kind to permit the reading of decimals of the smaller divisions onthe scale-plate 13. The zero-line 30 of the Vernier-scale is continuedentirely across the `face of the sliding block 27, and is exactly behindthe knife-edge 29 of the tubular bossy 28, so that in adjusting theinstrument it may conveniently be determined when the Zero-line 30 isprecisely on a level with the top of the mercury column by sighting pastthe knife-edge 29. The reservoir 14 has an open sideneckSl, and acloselyitting stopper 32is provided, which will ordinarily be insertedto prevent the entrance of dust and moisture.

When the device is to be used, the stopper 32 is removed for a fewminutes in order that the atmospheric conditions'within the reservoirmay correspond exactly with those of the surrounding air, after whichthe setscrew 24 is adjusted until the surface of the mercury in thereservoir is brought accurately to the tip of the pointer 26. Thevernier-plate 26 is then shifted. until the top of the mercury columncomes in line with the zero-point of the Vernier-scale and the knileedge29, when the reading is noted in the usual manner.

ln order that the jolting of the mercury within the tube and reservoirshall not do damage to the apparatus when the device is to betransported from place to place, the adjusting-screw 24 is raised untilthe flexible sack 1S is brought tightly in contact with the foot of thetube 11, as shown in dotted lines in Fig. 3. Under these conditions theglass tube 11 will be entirely iilled with a column of mercury, whichcannot escape, so as to jolt about and break the fragile parts of theinstrument. A lock-nut 33 is employed on the shank of the set-screw 24to insure its remaining in the desired adjusted position.

I claim as my invention 1. ln a barometer, in combination, an invertedcup; a tube extending upward from the cup and integral therewith, thelower end of the tube being prolonged into the chamber of the cup, a'flexible closure for the mouth of the cup; and means for llexing theclosure.

2. ln a barometer, in combination, an inverted cup having an outstandingilange at its rim g a tube extending upwardly from the cup and integraltherewith, the lower end of the tube being prolonged into the chamber ofthe cup; a Yflexible closure for the mouth of the cup; and means forllexing the closure.

3. In a barometer, in combination, a cup; a tube rising therefrom, thelower end of the tube being prolonged into the body of the cup; aZero-point projecting into the chamber between the cup and the tube andintegral with the wall of such chamber, and means for varying the levelof the liquid contents ot the cup.

4. In a barometer, in combination, a cup; a tube rising therefrom; aZero-point projecting laterally from the tube and integral therewith andmeans for varying the level of the liquid contents of the cup.

5. ln a barometer, in combination, an inverted cup having an outstandingflange at its rim,l a tube extending upwardly from the cup and integraltherewith, the lower end of the tube being prolonged into the chamber ofthe cup; a flexible sack at the mouth of the cup; a flanged base-plateand a ring for gripping the rim oil the sack and the flange of tne cup;and a set-screw extending through the base-plate and bearing against thesack.

6. A barometer provided with an indicating liquid-containing vesselhaving integral with it a Zero-point projecting into said chamber, andmeans for varying the level of the liquid. contents of the vessel.

ALEXANDER H. MCCONNELL.

Vitnesses JN0. M. ROBERTS, MARY DENisoN.

